CHAPTER VI.THE TERTIARY SYSTEM.
The Tertiary System forms the last great subdivision of the rocky strata of the earth—the last in the creative, as well as geographical, distribution of organic and inorganic matter—antecedent to the human epoch. All the European and partly Asiatic chains of mountains were again farther elevated toward the close of the preceding period. Europe itself assumed a more distinctive shape and contour, a bolder coast-line, higher plateaux, deeper and more extensive lakes. Great Britain was rounded into form, settled upon new foundations, and already stood out, in her western and northern belt of granitic and primary rocks, the empress of the ocean.
In thus recalling the features of the old world, and marking the configuration of a newer state of things, geology furnishes indubitable evidence upon which to establish these and other more general conclusions. The physical geography of the globe is inseparably connected with the series of changes we have been contemplating. The elevation, small and isolated as it appears, of the formation termed the wealden, supplies a key by which to measure the rivers and deltas of our own island. The chalk, forming at the time the bed of the ocean, remained for a period in undisturbed repose, as evidenced by the hollows and erosive action seen on its surface. Then a series of convulsive movements, over a vast area, are indicated by the disrupted and altered position of the strata, when the bottom of the sea was lifted up, and its whole marine fauna completely changed. The secondary era passed away: the new tertiary arrangements, animate and inanimate, from henceforth commence.
Thus rolls on the mighty course of time. A continent is thegift of one age: half a globe is shattered and wasted in the next. All living things become extinct and entombed in this quarter: in that, there are new and more abundant creations. The face of nature is again redolent with beauty: life, profusion, and enjoyment are everywhere abounding.
“Look down on earth. What seest thou? Wondrous things,Terrestrial wonders that eclipse the skies.Nor can the eternal rocks His will withstand—What leveled mountains, and what lifted vales!High through mid air, here streams are taught to flow—Whole rivers there, laid by in basins, sleep—Here plains turn oceans; there vast oceans join,Through kingdoms, channel’d deep from shore to shore.”
“Look down on earth. What seest thou? Wondrous things,Terrestrial wonders that eclipse the skies.Nor can the eternal rocks His will withstand—What leveled mountains, and what lifted vales!High through mid air, here streams are taught to flow—Whole rivers there, laid by in basins, sleep—Here plains turn oceans; there vast oceans join,Through kingdoms, channel’d deep from shore to shore.”
“Look down on earth. What seest thou? Wondrous things,Terrestrial wonders that eclipse the skies.Nor can the eternal rocks His will withstand—What leveled mountains, and what lifted vales!High through mid air, here streams are taught to flow—Whole rivers there, laid by in basins, sleep—Here plains turn oceans; there vast oceans join,Through kingdoms, channel’d deep from shore to shore.”
“Look down on earth. What seest thou? Wondrous things,
Terrestrial wonders that eclipse the skies.
Nor can the eternal rocks His will withstand—
What leveled mountains, and what lifted vales!
High through mid air, here streams are taught to flow—
Whole rivers there, laid by in basins, sleep—
Here plains turn oceans; there vast oceans join,
Through kingdoms, channel’d deep from shore to shore.”
The geological district upon which we now enter, embraces London as nearly the center of its range, from which in every direction, along every line of railway, sections of the tertiary deposits are laid open: cabinets of conchology are to be met with in every pit for forty miles around; and what facilities to visit and examine them all with the speed of the wind. Not a spot but may be reached at a wish, sections more than can be numbered are in every locality, and in half the time one makes the ascent of Schehalion, he has taken the circuit of several counties.
London! what can it be likened or compared to? Nothing is so unlike as a simile, and we need not try to describe this emporium of the world by a comparison. It is not Rome nor Thebes, nor Nineveh, nor Babylon, but more than them all in the stirring activities of mere animal existence—more boundless in wealth—more dominant in conquests—more all-embracing in commerce; as deep in its sins, arrogant in its pride, haughty in its supremacy, as Queen City of the nations. About twelve hundred souls are every week added to that dense mass of human beings. As many, nearly, are every week blotted from the sum of mortal existence. No metropolis on this mundane scene ever stood in a similar relation to all other nations and cities of the world, whose every wish, for weal or woe, so affected the destinies of all the families of men. A part of every one of them is therein concentrated. Not a tribe but has its representative. Not a specimen or production of human skill but is borne thither. Genius, wit, industry,ingenuity, are in all their most beautiful creative efforts indelibly embalmed; and were that mighty pile to be ingulfed in the bosom of the waters, out of which its foundations were recently lifted up, thegenus homowould, in all its entireness, be conserved together—the type and wonder of our own geological epoch.
This city, too, contains everything else that the world contains. A specimen of every living thing is here; and things which cannot live, but pine and die away from their native haunts, have been carefully preserved and skillfully arranged for the inspection of the curious. The kaleidoscope, in all its phantasmagoria of change and infinite diversity of hues, can display nothing half so various as the realities of nature; and types of the entire modern era, from the extinct Dodo to the recently-discovered Moas of Wanganui, are before you in all their diversified forms, from the misshapen and fantastic to the loveliest of earthly creations. When Adam gave names to the creatures of the field, they are simply said to have been “brought unto him to see what he would call them;” every tree pleasant to the sight grew out of the ground; and Eve, Milton beautifully represents
“went forth among her fruits and flowers,To visit how they prosper’d, bud and bloom,Her nursery; they at her coming sprung.”
“went forth among her fruits and flowers,To visit how they prosper’d, bud and bloom,Her nursery; they at her coming sprung.”
“went forth among her fruits and flowers,To visit how they prosper’d, bud and bloom,Her nursery; they at her coming sprung.”
“went forth among her fruits and flowers,
To visit how they prosper’d, bud and bloom,
Her nursery; they at her coming sprung.”
Here are all things once more assembled, and as the tree of knowledge no longer bars from the tree of life, we can innocently search into all the mysteries, and see all the qualities and shapes, of every earthly object.
Nor is London less privileged and distinguished by its geological treasures and multifarious condition of things beneath. The capital stands on the tertiaryEocenestrata, or last of the rocky series of the island. The pre-Adamic arrangements all here cease, the boundaries betwixt the old and the new world are here drawn. The age ofhumanitydawns. And, interred in the deposits immediately below, lie the last of a series of monsters which preceded man’s introduction upon the stage, and between whom and all his race an unequal war of merciless extermination must have prevailed. The reasoning animal, indeed, at once the most helpless and most potent of nature’s offspring, could but ill haveexisted under a constitution of the elements which fostered the Palæotheriums and Chæropotami of the tertiary age.
Neither the romance of geology nor the era of prodigies, therefore, are yet over. The curtain once more requires to be lifted from the dark regions of the past, ere we approach the arrangements, forms, and distribution of animal and vegetable life, of the epoch in which our own lot has been cast.
I.The Tertiary Groupconsists of a series of well-marked and closely connected beds of clays, sands, gravel, brecciated conglomerate, marls, and limestones; some of which are of marine, and some of fresh water origin—points only to be determined by their respective fossil remains. Some lithological distinctions may also be established; the marine deposits are less minutely laminated than those of the fresh water; and also, in general, the beds are thicker, and their sediments more confused in their arrangement. “Limestones, and fine light-colored clays,” says Mr. Phillips, “constitute the principal mass of the fresh water sediments; while sands, and blue and variously-colored clays, more particularly mark the marine depositions. The latter appear like the products of littoral agitation, as if the wearing of cliffs of older strata had furnished the materials of these newer rocks; while the former resemble the accumulations from the wasting surface of chalky and argillaceous countries.”
These deposits lie in hollows and depressions of the chalk formation, and constitute what is termed the London basin. A similar series of materials occur in Hampshire, separated from the former by the upraised edges of the subjacent strata, which, cropping out in like manner on the south, inclose them also in a basin-shaped area. The same arrangement prevails across the channel, where a suite of rocks referable to the same age liewithinthe chalks, and constitute the well-known Paris basin, whose remarkable remains were first brought to light from their tomb of ages in Montmartre by M. Brongniart and Cuvier, upward of thirty years ago. The Auvergne basins, in central France, are equally well characterized. And, stretching onward through southern Europe, the tertiary deposits occupy positions nearly similar; and allcomposed, with slight local variations, of kindred fossils and sediments.
Geology has been compared to history. We also see how it embraces the whole range of physical geography, restoring the land-marks of the past, and presenting pictures of the earth’s surface which the mere traveler can no longer detect. The rolling Thames, with town, spire, and villa nestling in every slope, and tunnel, bridges, and
“Crowded ports,Where rising masts an endless prospect yield,”—
“Crowded ports,Where rising masts an endless prospect yield,”—
“Crowded ports,Where rising masts an endless prospect yield,”—
“Crowded ports,
Where rising masts an endless prospect yield,”—
we seek in vain for on the geological map of the period. There were spice islands, with aromatic gales, palm trees, dates, turtles lazily pacing the sands, and crocodiles heavily climbing the banks, or plunging and gamboling in the deeper pools. A Polynesia, with a tropical climate and corresponding luxuriance of vegetable and animal life, occupied the intermediate regions of Europe and Western Asia. On the south and west a vast continent loomed over the main, whence, in part at least, the detrital matter of the several basins alluded to was derived; and there, too, in all probability, the source of the spasmodic action which successively elevated and depressed the bed of the sea on which were accumulating the tertiary deposits, and whose throes finally terminated in its own submergence, and upheaval of the south-east coast of Britain, and the whole of central Europe. Gulliver returned with a report of strange people, flying islands, and fertile descriptions of impossible monstrosities. Geology deals in a simple shifting of the scenes, new arrangements in the drama of creation, and is entitled to credit in its boldest assumptions, furnishing proof, as it abundantly does, from the existing wreck of those vanished realities to which it now assigns local habitation and name. London occupies the bottom of an ancient sea, whose spoils, six or seven hundred feet in thickness, are there to attest the fact; and for miles around, every excavation into the marine mass multiplies the evidence, and repeats the story of its existence.
The plastic and London clays constitute the lower beds of the series immediately above the chalk, and are nearly co-extensive intheir range. From Reading on the west, these sediments stretch eastward through the valley of the Thames along the right bank to Margate; on the left, they cover the entire district to Ipswich; and constitute a very large part of the soil of the adjacent counties from Norfolk to Hampshire, prevailing more especially through the central and eastern districts. Mr. Prestwick has recently shown, that the lower English tertiaries form several distinct subdivisions, each marked by different conditions, and these conditions indicating ancient hydrographical and palæontological changes of importance. A conglomerate bed of round flint pebbles, mixed with yellow, green, or ferruginous sands, extends almost uninterruptedly from the Isle of Wight to Woodbridge, in Suffolk; this bed underlies the London clay, intercalated betwixt it and the plastic clay, and forms a well-marked geological horizon, dividing this formation from the older Eocene deposits. It contains thirty known, and eight or ten still undescribed species of testacea, twenty of which are not found in the lower deposits, while all are nearly identical with those of the superior and London clay beds. The plastic formation thus embraces the London clay, as the chalk does both, which again in its turn is embraced by the oolites; whence the older andinferior systemsall widen, and extend successively as the bed of the sea was elevated; and hence the basins were gradually narrowed and contracted as they approached the last and closing ante-human epoch.
A kind of convergency in all this can be distinctly traced in the superficies of the earth to the state which it has now assumed. A similar approximation in its living inhabitants, as will immediately appear, can as clearly be pointed out to its present occupants. Intelligent will and design are equally manifest in the arrangements; for, however great the amount of change, the restraining hand of foresight is visibly present in them all, and, in every successive advance to the present order of things, a purpose is discernible in making the more effectual provision for the permanent stability of the human system.
II.The Organic Remainsof the tertiary deposits, if they possess not so much of antiquity as those which have already passed in review, are all the more interesting and worthy of attention, asthey admit of a closer comparison with the established order of things, and the laws now regulating the distribution of animal and vegetable life. The locality most fertile in the organic remains of this period is the small island of Sheppey, situated near the mouth of the Thames, which is not more welcomely descried by the home-bound mariner as a Pharos of light and safety from the howling waste of waters, than it has proved to the palæontologist a repository and beacon-light for determining the most recondite mysteries connected with almost every living thing, in sea or land, during the Eocene age. It consists entirely of the London clay deposit, of an average thickness of five hundred feet, and displaying in the cliffs vertical faces two hundred feet high. The fossils in both localities are almost identical; in the isle of Sheppey they are more abundant, as well as accessible; and, in consequence, they have been more minutely and generally described.
1. The shells are very abundant. A few genera have survived the changes and disturbances succeeding the upheaval of the chalk, and a single species of Gasteropodes (Actæon elongatus), is common to both formations. The Belemnites and Ammonites, swarming in the seas of the secondary period, are now entirely withdrawn. The Nautilus is but sparingly represented. The new genus Cerithium is introduced, a long, tapering, spiral-formed shell, and apparently of strong predaceous habits. Lobsters resembling existing species are very abundant. The Nummulites, of which entire rocks were formed during the secondary age, still survive. And, as an index to the state of temperature, it requires to be mentioned, that many species, now found only in tropical seas, are mixed with the testaceous fossils of these localities.
2. The fishes are equally peculiar and characteristic of the era upon which we enter. Nothing can more strikingly show the violence and universality of the change that was cotemporaneous with the tertiary arrangements, than the total disappearance of the old tribes of fishes, and their replacement by entirely new specific, and a large infusion likewise of new generic, types. The change is no less remarkable when viewed in its relation to existing races, every one of which, with the solitary exception of the salmon family, have here their representatives. Perch, cod, herring, mackerel, eels, had all become occupants of the seas of thisperiod, and their remains deposited in the clays of Sheppey are in the greatest profusion. “The number of fossil fish from the London clay,” says Agassiz, “amounts to ninety-two in the one single locality of Sheppey, without counting ten species to which I have not yet assigned names, not having hitherto been able to characterize them in a satisfactory manner.” The difficulty arises from two causes—the imperfect and fragmentary state of the fossils themselves, and the new principle adopted by him for their classification.
Most of the fishes belonging to the tertiary era are of the Cycloid and Ctenoid orders, with thin fragile scales, which, unlike the Ganoids whose cuirassed bodies were protected by a thick covering of plates, have been unable to preserve the integrity of their form and outline. The greater number of these interesting remains, accordingly, have rotted in the matrix, their bones separating, and the soft parts all replaced by clay. The scales aredisaggregated(leur sécailles désagrégées), and the cranium alone of the osseous structure remaining entire, owing to the soldering of the pieces composing it, the ingenious naturalist has adopted this single organ as the basis of the new system. “The characteristic features of the skulls of the mammalia and reptilia are known; the variations which such a bone, such a crest, such a groove may undergo in such and such a family are understood; and already, at the first glance, it is possible to ascertain whether the animal under consideration is carnivorous, ruminant, or solipedal. But nothing is more variable than the forms of the cranium and of the heads of fish. The multitude of bones and of spines which serve for the attachment of the muscles, the infinite variety of forms in the families themselves, impart such a diversity to the crania of the fish, that the ichthyologist frequently despairs of being able to reduce them to their respective types, and in fact a comparative craniology of fish does not exist. There is no one, that I know, who can tell at first sight, whether such and such a cranium belongs to a percoid, to a sparoid, or to a chetodontal type.”[8]
Isolated crania and detached vertebræ are nearly all that remainof the Sheppey fossils, and the conclusions established from them by M. Agassiz, are as follows, throwing new and important light upon the two last great and approximating geological epochs.
The English coasts, at present, are inhabited by one hundred and sixty-three species of fish, of which there are eighty-one genera, divided among six predominant families, while two or three are only occasionally domiciled. Sixty species belong to the order of Ctenoids, fifty to that of the Cycloids, and eleven to the Ganoids. The fossil distribution establishes the following results: of Ctenoids twelve species, eleven genera, and three families, of which the perch tribe is the most numerous; three genera of the Teuthiæ, a family essentially meridional, and occurring only in southern seas, a fact which shows a higher climatic condition of temperature than now exists in this latitude; thirty-two species of the Cycloid order, twenty-six genera, and eleven families—of these the cod and mackerel tribes are the most numerous. While no trace of the family Salmonidæ has been detected in the tertiary deposit, a family exclusively tropical, the Characidæ, is found to have had congeners of very considerable size in the more ancient epoch. The haddock, cod, and ling races are very abundant—a fact, says Agassiz, which proves that, notwithstanding the more meridional physiognomy of the Sheppey deposit as a whole, there is nevertheless already an approximation in the fish of this interesting locality toward the actual character of the ichthyological fauna of England.
The living representatives of most of these fossils are, if anywhere, to be looked for in southern and tropical latitudes; for, notwithstanding of an approximation, there is not much of real identity of type between the existing and extinct races of the British seas. In fact, there are but four genera,Megalops,Cybium,Tetrapterus, andMyripristis, whose families are still known in the current epoch; and but very few species, from the rich prolific beds of Sheppey, have been as yet rendered into living forms.—The fishes most nearly related to the present inhabitants of warmer climes are those which are obtained from the fossil tertiary deposits of Monte Bolca in northern Italy, and in the little explored region of Mount Lebanon. Much remains to be done, therefore, before wider generalizations can be fully established.The knowledge already acquired in this department of ichthyology confirms every previous inference relating to periodic physical changes of the globe, and their convergency to the order and arrangements of nature which now prevail over the earth.
3. The reptiles and semi-natants of the tertiary period lead to the same general conclusions. The intercourse now so closely established betwixt this country and Borneo throws new light, every day more and more, upon the ancient condition of our island. The resemblance, both in the fauna and flora of these remote places, is striking throughout; when, forspaceon the one hand we substitutetimeon the other, we have nearly a transcript of their respective conditions. The northern swarmed with the crocodiles of the southern hemisphere: the boa constrictor has his representatives in the serpents of the London clay; and turtles, both of marine and fresh water characters, are equally abundant. The Pythonic monster is also there, represented by reptilians which now only inhabit tropical countries, and prey on quadrupeds and birds, both of which became abundant during the tertiary age.
4. The mammalia consisted of large pachyderms or thick-skinned animals, now represented by the rhinoceros, tapir, and elephant. Wolves, foxes, and raccoons, mice, rats, rabbits, hogs, even monkeys, began also to flit over the stage of stirring life. The existence of the order Quadrumana and the ape genus Macacus, during the earlier tertiary period, was determined by the discovery of the fragment of a lower jaw, including the socket of the last molar tooth, in a stratum of blue clay in Suffolk, and described in the “Magazine of Natural History,” for 1839, by Professor Owen. Other remains have been detected of the same animal in France, the East Indies, and South America, establishing beyond a doubt the co-existence of four different genera of apes and monkeys with the extinct mammalians of the English tertiary deposits.—That these creatures were anterior toMan, in point of creation, is in accordance with all geological evidence regarding the animal kingdom. The progressive development theory avails itself of the fact, but can establish less upon it than if it took the example of the bat—which, in anatomical structure, resembles the human family scarcely less than the monkey! But geographicallyconsidered, it furnishes a striking instance of the wonderful revolution which this island has undergone since the comparatively recent epoch of the tertiary formation. Images and pictures of life are thus called up in the vista of the past, which at once transport the mind into the bosom of the wilderness or remote Afric forest; and long ere man had betaken himself to cities, or a stone of all that huge capital had been dug out of the earth, or a sail of all its vast commercial greatness had been wafted over the waters, the very spot on which he has developed the greatest resources of his power, enterprise, and genius, was tenanted by those tribes which approach him nearest in form, which philosophers have mistaken for his type, but in which the semblance of external figure is lamentably contrasted by the absence of all that moral framework, mind, and spirit, which pre-eminently distinguish and glorify the human race!
A remarkable peculiarity in the mammalian remains of the tertiary period is the total absence of the ruminating animals, which do not appear until the modern epoch, when we recognize them at once as the companions and useful contributors to the comforts of man. These still retain “the names” which Adam bestowed upon them. The more ancient creations rejoice in the mythical nomenclature of science, of which between fifty and sixty species have been determined. The greater proportion are from the Paris basin; but the district under review contains, in its lower and middle divisions, the remains of some of the more remarkable of the group—as thePalæotherium,Anoplotherium,Lophiodon,Chœropotamus,Didelphis,Balœenodon, and the hugeMastodon.—These animals are specifically different from everything now in existence; even Macacus Eocenus will find no lineal descendant in Ceylon, Madagascar, or the Cape; and no Celtic pedigree will meet the case. The race have left our island, and departed from the earth; and to restore them in imagination, we must seek their nearest analogies in the impenetrable fastnesses and prairies of unreclaimed nature.
5.Birdsare distinctly traceable in this formation. The Eocene clays of the Isle of Sheppey have produced materials sufficiently indicative of the class, in which the true affinities of the aerial inhabitants are detected, and a new genus completely established.The specimens found bear a resemblance to the osteology of the smaller kinds of vultures, and one has been designated Lithornis Vulturinus. The ‘Icones fossilium sectiles’ of Kœnig contains a description of some other ornitholites found in the same locality, considered by the author as belonging to a natatorial or long-toed bird, and denominated Bucklandium Diluvii. The Paris basin is more fruitful in these fossils than the London; from these several species have been determined—more or less allied to the pelican, the sea-lark, curlew, woodcock, buzzard, owl, and quail; thus clearly establishing the link in the chain of being, but still at a wide interval from the gay choristers and domesticated tribes which minister so much to the solace and happiness of man. The geologist traces the connection, and sees in the expanse of ages, as race after race emerge upon the scene, a gradual preparation and tendency of all things to a final result; sea, earth, and air successively possessed by creatures approximating as they advance to those of the human epoch; and man proudly or presumptuously concludes, that all has been “worked solely for his good.” But as the poet has sung—may we not ask, and ask concerning the humblest life which man often despises and as often terribly destroys, but which is never overlooked by Him who made man and all things, and whose tender care is over all his works?—
“Is it for thee, the lark ascends and sings?Joy tunes his voice, joy elevates his wings.Is it for thee, the linnet pours his throat?Loves of his own, and raptures swell the note.Is thine alone, the seed that strews the plain?The birds of Heaven shall vindicate their grain.”
“Is it for thee, the lark ascends and sings?Joy tunes his voice, joy elevates his wings.Is it for thee, the linnet pours his throat?Loves of his own, and raptures swell the note.Is thine alone, the seed that strews the plain?The birds of Heaven shall vindicate their grain.”
“Is it for thee, the lark ascends and sings?Joy tunes his voice, joy elevates his wings.Is it for thee, the linnet pours his throat?Loves of his own, and raptures swell the note.Is thine alone, the seed that strews the plain?The birds of Heaven shall vindicate their grain.”
“Is it for thee, the lark ascends and sings?
Joy tunes his voice, joy elevates his wings.
Is it for thee, the linnet pours his throat?
Loves of his own, and raptures swell the note.
Is thine alone, the seed that strews the plain?
The birds of Heaven shall vindicate their grain.”
6. And in the Flora which then decked the plains, fringed the marshes, or clothed the heights, “the birds of heaven” had ample provision in seed, fruit, and herbage for all their wants. Remarkable indeed the adaptation of the animal tribes referred to in the previous section to the lacustrine condition of the surface which still so generally prevailed. The plants of the period are such as are now exclusively confined to warm or tropical latitudes. The palms and cocoa-nut bearing trees are abundant andof different kinds. One family belongs to theNipadites, which are found in Japan and the Spice Islands, generally in the estuaries of rivers, or along the tracts of damp marshy grounds. The lovely Acacia was here naturalized. Pepper, dates, and cucumbers added to the variety of the sylvan banquet, which tall branching pines shaded from the scorching heat. If we are no longer in possession of the luxurious fruits and condiment-bearing plants of this early age, the change has led to other and better productions. For deep lakes we have these verdant meadows and corn plains; the stagnant marshes are drained of their mephitic vapors; the theroid monsters are supplanted by the laboring ox and the industrial horse; and with all the arts flourishing, and carried to the highest pitch along her borders, the proudest achievements of science wafted on her bosom—the “fruitful Thame” may challenge the nations of the earth for every product which climate yields or genial suns ripen.
Such was the dawn or introduction to the present order of things. In the language of geology it is called theeocene ageof the world, because it approaches in its organic productions to those which are now existing, and containing a very few recent species, not more than three or four per cent. Nature did not all at once leap from one epoch to another. In the tertiary deposits there is evidence of successive creations, rests and pauses, as it were, before the final and crowning consummation of her works. More and more analogies begin to manifest themselves in the ascending series of the group. The Miocene, or middle period, develops a yet larger proportion, though not a majority, of the present inhabitants of the sea. The Pleiocene arrangements follow; and in the shells and terrestrial products of this group the modern characters and types are still more clearly discernible. When we reach the highest members, the difficulties of separation from the modern deposits begin to multiply; the mineral qualities and mere earthy beds are not distinguishable; while, on the other hand, in all the animal forms and huge colossal proportions of Mastodons and Theriums, there are the unequivocal markings of an extinct anterior age.